How Many 4 Speeds?
 

Back in the late 60's and early 70's 4 speeds were standard and 5 speeds were an option. Is there any info on how many 4 speeds and 5 speeds were actually produced for each year. I notice most early 911's being advertised are 5 speeds, rarely do you see a 4 speed.

This may be a stupid question but I also noticed that the ratio's for 1st and 4th on a 4 speed and the same as 1st and 5th on a 5 speed. So other than during accelleration is there any advantage to the 5 speed. I assume since the ratios for the top gear are the same the rpm's would also be the same say when freeway/highway driving? Or maybe the rear axle was different?

Thanks

The US was the largest market back then with more than half of the cars coming here. Americans wouldn't buy a sportscar with a 4spd gearbox, so most dealers optioned the cars as 5spds when ordering their stock.

You see a fair number of 912s with 4spds, but in general, most North American 65-73 911s got 5spds. If anyone has an idea on the numbers it would be Dave Pateman. I suspect he'll see this thread within a day...

5spd offered better acceleration. That is the sole advantage. Both the 4spd and 5spd got the same 7:31 ring and pinion. The exception is the 1969 912, which got a 5spd with a short ratio 6:29 ring and pinion. Pretty rare gearset these days. Some racers like them, but they wear out quickly. They are also a different size differential so they take a really super rare LSD to make them a proper racing final drive. The factory used them for hill climb cars.

Thanks Matt. Hopefully we will hear from Dave Pateman.

If the only advantage between the 4 and 5 speeds was acceleration, would the 4 speed not have been faster as you would have had fewer gears to pass through to get up to speed?

The difference is the gearing advantage of the 5-spd (closer ratios and higher torque multiplier) put the engine in the peak torque-peak power band for more of the acceleration run. This more than offsets the delays of shifting. That said, you're correct that shifts take time to complete and more shifts = more time so that takes away some of the gains from the more optimal gearing.

More of a factor on a road course where gear selection is more critical to acceleration off a corner.

So I guess there is no data on how many 4 and 5 speeds were produced?

Not sure about the data, but besides 912s, 911T's would have come with a 4spd unless optioned with a 5speed. Many 4spd T's have subsequently been converted to 5spd cars.

Suprisingly, a few years back when I considered a longhood I came across TWO 4spd T's.